<HTML><HEAD><TITLE>+(+Number, -Result)</TITLE>
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<H1>+(+Number, -Result)</H1>
Checks if Number is a number and unifies it with Result.


<DL>
<DT><EM>Number</EM></DT>
<DD>A number.
</DD>
<DT><EM>Result</EM></DT>
<DD>A variable or a number.
</DD>
</DL>
<H2>Description</H2>
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to +(Number, Result) is equivalent
   to
<PRE>
    Result is +Number
</PRE>
    which should be preferred for portability.
<P>
   Number and Result have to be of the same type.

<P>
   In coroutining mode, if Number is uninstantiated, the call to +/2 is
   delayed until this variable is instantiated.

<P>

<H3>Modes and Determinism</H3><UL>
<LI>+(+, -) is det
</UL>
<H3>Exceptions</H3>
<DL>
<DT><EM>(4) instantiation fault </EM>
<DD>Number is not instantiated (non-coroutining mode only).
<DT><EM>(24) number expected </EM>
<DD>Number is not of a numeric type.
</DL>
<H2>Examples</H2>
<PRE>
Success:
      +(1, 1).
      +(5, Result).        (gives Result = 5)
      +(-6.2, Result).     (gives Result = -6.2)
Fail:
      +(1, 0).
      +(1.0, 1).
      +(1, 1.0).
      +(1, r).
Error:
      +(A, 6).                   (Error 4).
      +(4 + 2, 6).               (Error 24).



</PRE>
<H2>See Also</H2>
<A HREF="../../kernel/arithmetic/is-2.html">is / 2</A>
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